In selector transmissions of countershaft design, particularly for industrial vehicles, the center distance between the main shaft of the transmission and the countershaft constitutes a central factor. The greater the torque to be transmitted, the greater the center distance has to be selected. At the same time, the center distance should be laid out rather small for the higher gears, that is, for low ratios and rather large for the lower gears, that is, for high ratios. The center distance is a compromise between the ideal dimensions of the individual ratio steps.
One other general condition for the selection of the center distance in selector transmissions is constituted by tying of a power takeoff in industrial vehicle transmissions, especially in range transmissions having planetary drive as group transmission. The center distance must be selected large enough to make passing the adapter shaft for the power take off possible past the parts connected with the main shaft such as a planetary gear set.
Depending on the structural configuration of the transmission and the support of the shafts provided therein, an adapter shaft is situated between one countershaft and one power takeoff, the adapter shaft being coaxial with the countershaft and connected therewith via a spline section for torque transmission. In order that the power takeoff and the main output of the transmission can be provided next to each other, a minimum distance must be kept between the adapters on the power takeoff and on the main output connected with a prop shaft, which minimum distance has to be taken into account in the construction. This, in turn, requires on the shaft gear wheels with correspondingly large diameters and weight, which has a disadvantageous effect upon the total weight of the transmission.
In order to keep the center distance between the shafts small, it is thus already known, for example, to actuate the adapter shaft via a spur gear toothing such as the intermediate wheel of the reverse gear so as thereby to arrange the direction of rotation of the adapter shaft, according to the direction of rotation of the countershaft. Thereby an additional gearing has to be mounted on the adapter shaft and the adapter shaft needs additional support. To be able to absorb the torques of the power take off, the supports of the intermediate wheel of the reverse gear must be made reinforced accordingly. The toothing of the intermediate wheel of the reverse gear must thus be laid out on the power takeoff and the stress thereof.
In the applicant's still unpublished DE 100 39 314, a vehicle having a power takeoff shaft is described which comprises one adapter shaft connected with a countershaft parallel with the main output shaft of the vehicle transmission. The adapter shaft is disposed at an angle to the countershaft so that the distance of the power takeoff connection on the output of the vehicle transmission from the axis of rotation of the main output shaft is greater than the center distance between the axis of rotation of the countershaft and the axis of rotation of the main output shaft. The connection between the countershaft and the adapter shaft has a spline section, specially a section with a spiral toothing.
Departing from the above cited prior art, the problem on which this invention is based is to make possible a variable center distance between the main shaft and the countershaft of a selector transmission overcoming the disadvantages of the prior art. In a selector transmission of standard countershaft design, the center distance on the constant ratio on the input side must be smaller and in case of high ratios, the center distance on the output side must be larger. Besides, in a selector transmission with power takeoff, the distance of the power takeoff flange from the main shaft should be increased or independent of the established center distance.